Grid design optimisation for field emission neutralisers using carbon nanotube arrays

Abstract

Due to the rise in demand for nanosatellites in recent years, there has been increasing interest in integrating Hall Effect Thrusters (HETs) to provide propulsion capabilities. A key mission enabler for such HETs is a matching neutraliser to neutralise the ejected ion plume. At present, neutralisation exists for low-power classes (<10 W) and high-power classes (>100 W) of HETs. Carbon Nanotube Field Emission Neutralisers (CNT-FEN) have the potential to bridge the gap and provide neutralisation capabilities to intermediate power classes of HETs. Here, we attempt to optimise the grid design of the CNT-FEN by varying the Open Area Ratio (OAR) and the slit area of the gratings. The performance of the varied grid designs is measured through the emission current and the efficiency. Our results indicate that generally, optimal performance of the CNT-FEN occurs at an OAR ranging from 0.90 to 0.92, and a slit area ranging from 2.5 and 4.0 mm2. Using these optimal grid design parameters will improve the performance of the CNT-FEN, thus further solidifying their place as a neutraliser for intermediate power classes of HETs. In addition, future research into the CNT-FEN will now be able to start at a higher performance baseline.